3.2.3 Normalisation

Question 1

What is normalisation

Answer 1

logical process to work out correct structure of a database.

Question 2

Advantages of normalisation

Answer 2

less data duplication-

data redundancy reduced

data consistency improved

data integrity increase

Question 3

Disadvantages of normalisation

Answer 3

complex

more tables

complex relationships between tables

more tables means the queries might be slow to run

Question 4

Functional dependency

Answer 4

the fact about an entity that can lead to others being worked out.

Question 5

Data dictionary

Answer 5

‘a centralised repository of information about data such as meaning, relationships to other data, origin, usage and format’

last stage in planning process

data about data

field names data types field size format default value table names key field details validation.

Question 6

Compare and contrast ER modelling and normalisation as approaches to developing a relational database.

Answer 6

ER modelling uses ER diagrams to represent real world objects and the links between them.
Normalisation is a technique of organising the data in the database to eliminate problems such as data redundancy and data inconsistency and improving data integrity.
Compare
Both methods can be used in the design stage. They both identify entities and relationships.
Contrast
ER modelling is a graphical approach to database design. Normalisation follows a set of decomposition rules.